drawing a stratified sample in R

Question

Designing my stratified sample

library(survey)
design <- svydesign(id=~1,strata=~Category,  data=billa, fpc=~fpc)

So far so good, but ho

Answer 1

here's a quick way to sample three records per distinct 'carb' value from the mtcars data frame without replacement

# choose how many records to sample per unique 'carb' value
records.per.carb.value <- 3

# draw the sample
your.sample <- 
    mtcars[ 
        unlist( 
            tapply( 
                1:nrow( mtcars ) , 
                mtcars$carb , 
                sample , 
                records.per.carb.value 
            ) 
        ) , ]

# print the results to the screen
your.sample

note that the survey package is mostly used for analyzing complex sample survey data, not creating it. @Iterator is right that you should check out the sampling package for more advanced ways to create complex sample survey data. :)